Hydraulic vibratory jar



July 14, 1959 T. A. ANDREW HYDRAULIC VIBRATORY JAR Filed sept. 7, 1956 2 Sheets-Sheet 1 INVENTOR.

/I'Il l (.4 l 1 4free/vnf July 14, 1959 T. A. ANDREW 2,894,724

HYDRAULIC VIBRATORY JAR Filed Sept. 7, 1956I 2 Sheets-Sheet 2 ZZ/oMAJ A', ,4A/025W ,1. 4free New States Patent 'I'his invention relates to sub-surface oil well equipment and particularly to a vibratory hydraulic jar.

In the drilling and maintenance of wells it is frequently desirable or necessary to apply a series of impacts or vibrations to equipment in the well bore. For example, tools or well bore liners which have become fast in the Well bore are most readily retrieved by the simultaneous application of an upward strain and a series of rapid impacts or vibrations on the tool or liner. Also, it is known that the cutting action of a rotary drilling bit is rendered more effective if the bit is axially vibrated during rotation, and that the use of vibrations during the placement of cement in a well bore is effective to produce a superior cementing bond. In the case of casting cement in a mold, the vibration of the mold results in a casting of higher quality, density, and homogeneous cross. section.

Most jars which have been devised employ a relatively massive hammer for producing the impacts. The impacts of these existing jars are, therefore, substantial in magnitude but may be generated only at an extremely low frequency whereas it is well known that in all the above mentioned applications, maximum effectiveness of the jar is achieved by 'lighter impacts or vibrations of higher frequency. Thus, jars for use in fishing and drilling operations are most effective when they produce a series of sharp, rapid impacts more in the nature of a vibration than a sen'es of individual impacts. Moreover, most rapid removal of the sh is accomplished when a steady strain is maintained on the latter during the vibrating action.

Most existing jarring techniques, on the other hand, necessitate the release of the fish during a portion of the impact cycle so that it settles slightly in the well bore after each impact. Accordingly, a portion of the energy of each subsequent impact is, in effect, wasted in raising the fish the slight distance which it settles during this brief instant of release.

An object of this invention is the provision of a well jar for producing a series of sharp impacts in rapid succession or a pulsating action for use in lishing, drilling and sealing operations.

Another object of this invention is the provision of a vibratory well jar of the class described which is hydraulically operated by the well fluids which are commonly pumped into the well bore during fishing, drilling and sealing operations.

Yet another object of the invention is the provision of a hydraulic, vibratory well jar of the class described for imparting vibrational impacts to a iish during a lishing operation and which permits a steady upward strain or pull to be maintained on the sh during vibrating of the latter.

A further object of the invention is the provision of a hydraulic, 'vibratory jar of the class described which is effective to furnish a series of rapid impulses to a drilling bit so as to secure a more effective cutting action of the drill bit.

ICC

Yet a further object of the invention is a provision of a hydraulic, vibratory jar of the class described which is capable of producing a pulsating action during well cementing operations so as to secure more effective placement and setting of the cement slurry.

A still further object of the invention resides in the provision of a hydraulic vibratory jar of the class described which is relatively simple in construction, inexpensive to manufacture, and has a minimum of moving parts so as to be less prone to maloperation and require less servicing than existing jars of this character.

Briefly, the foregoing objects and advantages are achieved, in the illustrative embodiments of the invention, by the provision of a sleeve mounting box and pin connectors for coupling of the sleeve in a string of drill pipe and the like. A piston, slidable in the sleeve, is formed at its upper end with a series of axially extending, flexible valve lingers which in normal unstressed condition are spaced slightly from the inner wall of the sleeve. Biasing spring means operatively engaged between the sleeve and piston bias the latter to a normal upper limiting position wherein the upper ends of the valve lingers are located slightly above a series of discharge ports formed in the sleeve.

The box and pin couplers carried by the sleeve have central passages to accommodate the flow into the jar of well liuids, such as mud or cement, pumped through the drill or fishing string from the surface. Flow of this fluid through the restricted space between the valve ngers and inner wall of the sleeve to the discharge ports in the latter produces a pressurerdilferential across the fingers causing them to be flexed outwardly into sealing engagement with the discharge ports.

This sealing of the discharge ports results in an inV crease of pressure above the piston causing the latter to be moved downwardly in the sleeve against the action of the biasing spring means. During this downward movement of the piston, the discharge ports are uncovered by the valve lingers so as to permit substantially unrestricted flow of the lluid from the sleeve through such ports and return of the lingers to their normally unstressed condition. The piston biasing spring means then becomes effective to return the piston upwardly to its normal position in response to the drop in pressure above the piston whereupon the foregoing cycle is repeated.

In one form of the present jar, especially designed for use in fishing operations, the piston and sleeve carry cooperating impact surfaces which are arranged to strike during return of the piston to its normal position under the action of the biasing spring means. In another illustrative form of the invention, especially designed for cementing operations, the impact surfaces are omitted and the piston is retained in normal position by a pair of oppositely directed compression springs. During operation of the device, the piston is reciprocated against the action of the biasing springs to produce a generally pulsating action rather than a series of distinct impacts. In a third illustrative form of the invention, the piston and sleeve carry pairs of cooperating impact surfaces which are arranged to strike blofws during both the upward and downward movements of the piston as is desirable, for example, in drilling operations.

In each of the illustrative forms of the invention, the relatively steady llow of fluid from the surface to the jar is converted to a pulsating flow of fluid from the jar to the fish or drill bit, as the case may be or in a pulsating llow of cement resulting in more effective uti-V lization of the iluid for its intended purpose.

Other objects and advantages reside in certain novel features of arrangement and construction of parts as will become apparent from the following detailed description taken in connection with the accompanying drawings wherein:

Fig. 1 is a longitudinal section through one form of the present jar shown the parts of the latter in one position of operation;

Fig. 2 is a partial longitudinal section through the jar of Fig. l showing certain parts of the latter in another position of operation;

Fig. 3 is a view similar to Fig. 1 illustrating the parts of the jar in a third position of operation;

Figure 3a is a section taken along line 3a-3a of Fig. 3;

Fig. 4 is a section taken along line 4-4 of Fig. 1;

Fig. 5 is a section taken along line 5-5 of Fig. 2;

Fig. 6 is a view similar to Fig. 2 illustrating the final operative position of the parts; and

Figs. 7 and 8 are longitudinal sections through modified forms of the present jar.

'Referring now to these drawings and particularly to Figs. 1-6, there is illustrated one form of the present jar which is designed to strike a sharp upward impact as is desirable, for example, in retrieving articles which have become fast in a `well bore. The jar shown comprises an elongate sleeve mounting an upper coupling box 22 and a lower coupling pin 24 for attachment of the sleeve in a fishing string, as illustrated. The box 22 and pin 24 have central passages 23 and 25, respectively, to accommodate the flow of mud from the surface, into the sleeve 20 through the section of drill string 26 extending from the surface to the sleeve, and from the lower end of the sleeve to the fish, not shown, through the section of drill string 28 extending from the lower end of a sleeve.

Indicated at 30 is a piston including an intermediate cylindrical portion 32 which is slidably received within the sleeve 2t?. An Oring 34 contained within an annular groove in the portion 32 slidably seals the latter to the inner wall of the sleeve 2f). The lower end of the piston is externally reduced at 36 and encircled by a coil compression spring 38 which bears at its upper end against the annular shoulder 40 at the juncture of the reduced portion 36 and cylindrical portion 32. The lower end of the spring 38 seats on an annular shoulder 42 of the sleeve 20 through a central opening 43 in which shoulder the reduced portion 36 slidably extends. As shown most clearly in Fig. 3a, shoulder 42 comprises a ring which is rigidly bonded to the internal wall of sleeve 20 and formed with a series of axially extending air ports 43.

Piston 32, is therefore, biased upwardly in the sleeve 20 by the spring 38, such upward movement being limited by abutment of a collar 44, rigid on the lower end of the portion 36, with the shoulder 42. During operation of the jar, as will be presently described, the collar i4 strikes the shoulder 42 to produce an upward impact. Accordingly, in the ensuing description, collar 44 and shoulder 42 will be referred to as a hammer and an anvil, respectively.

In the normal or upper limiting position of the piston 30, its upper end is located a slight distance above a series of discharge ports 46 in the sleeve 20. The upper end of the piston is externally reduced and centrally bored to provide a relatively thin walled section which is longitudinally slotted so that there are formed a plurality of relatively thin, flexible valve fingers 48.

In their normal unfiexed condition, these valve fingers S are spaced slightly from the inner wall of the sleeve 20 to form a restricted annular iiow space 49 communicating with ports t6 when the piston 30 is in its normal position. Space 49 and ports 46 define a passage, in the normal position of the piston, communicating the space above the piston to the exterior of the sleeve 20. Fluid entering the sleeve 20 through its upper end may, therefore, iiow through this passage 49, 46 when the piston is in normal position. Fixed in the sleeve 249 a distance above the upper ends of the fingers 48, when 4l the piston 343 is in its upper limiting position, is a disk 5t) formed with a central orifice 52. A reduced central passage 54 in the piston communicates at its upper end with the enlarged bore in the upper end of the piston and opens through the lower end of the latter to accommodate the ow of fluid through the piston.

In operation of the jar just described, mud or other fluid will be pumped from the surface downwardly through the fishing string 26 into the sleeve 20 whence it will iiow through the orifice 52, in the orifice plate 50, to the piston 30. A portion of this mud flows through the central passage 54 in the piston and through the lower section of fishing string 28 to the overshot or other fishing tool (not shown) and is discharged through the ports in the tool prior to engagement of the latter with the fish to be retrieved. This discharge of mud from the tool tends to clear the settlings away from the fish so as to enable proper engagement of the fishing tool therewith. Upon engagement of the tool with the fish, which, for example, may be a drill bit, ports in the tool are placed in communication with the passage through the drill bit, in the well known manner, so that fluid will be forced to ow through drill bit and out the lower end of the latter to aid in the removal thereof.

The remainder of the mud entering through the orifice 52 fiows through the passage 46, 49, that is between the valve fingers 48 and the inner wall of sleeve 20 and out the discharge ports 46, into the well casing S6. This ow of mud between the valve fingers 48 and the sleeve 20 creates a pressure differential across the fingers which causes flexing of the latter outwardly-against the inner wall of sleeve 2@ to seal the discharge ports 46, as shown in Fig. 2. Continued fiow of mud through the orifice 52 with the valve fingers 4S in this sealing position, increases the pressure of the mud above the piston 30 with resultant downward movement of the latter, against the action of the biasing spring 33, to the position of Fig. 3.

In this lower position of the piston, the upper ends of the valve lingers 48 are below the discharge ports 46 so that substantially unrestricted ow of mud occurs through the discharge ports 46 into the well casing. TheV pressure above the piston 30 is, thereby, relieved and is further reduced owing to the pressure drop attendant to the increased rate of flow through the orifice 52 resulting from complete uncovering of the discharge ports 46.

The parts are so designed that the pressure above the piston at this stage in the operation of the jar will be substantially less than the upward force exerted by the now compressed biasing spring 3S. The piston 36 is, therefore, moved upwardly by the spring to bring the hammer 44 into sharp impact with the anvil 42 so that an upward blow is transmitted through the lower section of the drill string 2S to the fish being retrieved.

During the initial downward movement of the piston, the valve fingers 43 will remain in their outwardly fiexed position until their upper ends have cleared the ports 46 whereupon they will return to their normal, unstressed position. Upon upward movement of the piston under the action of spring 38, the valve fingers remain in their unstressed positions spaced from their inner wall of sleeve Ztl, as shown in Fig. 6, and flow of mud again occurs between the valve fingers 48 and the inner wall of sleeve 29 with resultant outward'flexing of the fingers i8 to seal the ports 46 and repetition of the above de-V ment with the ports 46, the lower reduced portion 36 of the piston 30 and the opening 43 in the anvil 42 are preferably squared.

The jar illustrated in Fig. 7 is especially designed for use during sealing and cementing operations and is arranged to produce a pulsating action to facilitate placement of the cement slur-ry in the bore and settling of the slurry into a more dense and homogeneous mass. The jar of Fig. 7 is generally similar to that of Figs. 1-6 and comprises a sleeve 54 in which is fixed an orifice plate 56 having a central orilice 58. Axially movable in the sleeve 54 below the orice plate is a piston 60 formed at its upper end with exible valve fingers 62 identical to the valve fingers 48Vin Figs. 1-6 and which serve to alternately seal an open discharge port 64 in the sleeve 54 in precisely the same manner that the valve lingers 48 alternately seal and uncover the discharge ports 46 in Figs. 1-6.

The lower end of piston 60 is externally reduced at 66 and extends loosely through an opening 67 formed by an internal shoulder- 68 on the sleeve 54. This shoulder is identical to shoulder 42, previously described. A pair of coil compression springs 70 and 72 encircle the reduced piston portion 66 at opposite sides of the shoulder 68, the upper one of these springs seating against the shoulder 68 and against the shoulder 74, at the juncture of the lower reduced portion 66 and upper enlarged portion 76 of the piston 60. The lower spring 72 seats at its upper end against the underside of the shoulder 68 and at its lower end on a collar 78 xed on the lower end of the piston so that the latter is normally biased to the position of Fig. 7 wherein the upper ends of the valve fingers 62 are located slightly above the discharge ports 64. The piston 60 carries an O-ring seal 79.

Operation of this latter form of the invention is substantially indentical to that previously described, except that in the case of the jar of Fig. 7, cement slurry, rather than mud, will be pumped from the surface to the jar. This cement slurry enters through the orice 58 and ows between the valve iingers 62 and the inner wall of sleeve 54 to the discharge ports `64, thereby causing outwardv flexing of the Valve fingers 62 to seal the opening 64 and cause downward movement of the piston 60, as in the case of the jar of Figs. l-6. Downward movement of the piston 60 compresses the upper biasing spring 70 so that upon uncovering of the discharge ports 64 by the valve iingers 62, the piston will be moved upwardly in the sleeve 54 by the spring 70. The energy of the upwardly moving piston is absorbed by the lower biasing spring 72 so that there is transmitted to the section of drill pipe (not shown) attached to the lower end of the jar a generally pulsating action.

A portion of the cement slurry entering the sleeve 54 ows through a central passage 80 in the piston to the space below the piston while that portion of the cement which is intermittently discharged through the ports 64 flows through the annular space 82 between the sleeve 54 and an outer shell 86 sealed at opposite ends to the sleeve 54 and thence through lower ports 88 into the sleeve 54 below the piston 60. The slurry then ofws through the section of drill pipe (not shown) attached to the lower end of the sleeve 54 to the desired zone of placement of the slurry. This lower section of drill pipe will, in the conventional manner, be sealed to the well casing at some point. The pulsating action of the jar is transmitted to the casing through this seal to facilitate placement and settling of the slurry.

The form of the invention shown in Fig. 8 is designed to produce both upwardly and downwardly directed impacts as is desirable, for example, in drilling as well as lishing operations, and is substantially identical to the pulsating jar of Fig. 7, differing from the latter only in the omission of the outer shell 86 and the ports 88 and by the addition of a pair of upwardly and' downwardly extending cylindrical hammers 90 and 92 on the piston 94 which is otherwise identical to the piston 60 of Fig. 71.' The lower one of these hammers 92 is normally retained in engagement with the shoulder or anvil 68 to limit upward travel of the piston.

The piston 94 is caused to reciprocate by the action' of the flexible valve lingers 62 at the upper end of the piston in precisely the same manner as the pistons in the previously described embodiments of the invention. During initial downward movement of the piston to compress spring 70, the upper cylindrical hammer isV brought into impact with the anvil 68 to produce a downwardly directed blow. Upon subsequent upward movement of the piston under the action of spring 70,` the lower cylindrical hammer 92 is impacted with the anvil 68 to produce an upward blow.

It will be apparent that by designing a jar of any one of the forms described having a piston of appropriate size and mass, biasing springs of the proper spring constant, ports of correct size, valve fingers of appropriate stiffness and so forth, a resonant condition of operation may be established over a fairly broad range of operating fluid flow and'pressure. Moreover, the eiectiveness of the jar as a vibrating or oscillating device to produce cyclic displacement of other elements run in connection with it is enhanced and amplified by the motion produced in synchronism with it due to the previously mentioned pressure uctuations. The drill pipe or tubing supporting the jar constitutes an elastic member which responds to pressure changes within it. In other words, the supporting pipe lengthens with increased pressure and shortens with lessening pressure, thereby lowering and raising the jar in synchronism with its operation.

From the foregoing description, it will be apparent that there has been described a jar which is fully capable of attaining the objects and advantages preliminarily set forth. While preferred embodiments of the invention have been disclosed for illustrative purposes, it will be evident that numerous modifications in design and arrangement of parts is possible within the scope of the appended claims.

I claim:

l. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a uid inlet through which pressure uid may low into the interior space of the sleeve between said one end of the latter and the adjacent end of the piston, the wall lof the sleeve having a port through which said fluid may flow from said space, means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said adjacent end of the piston overlies said port, said piston being movable toward the other end of said sleeve against the action of said spring to a second position wherein said port is uncovered, there being a passage including said port communicating said space to the outside of said sleeve when said piston'is in said normal position, and valve means carried on the piston for closing said passage in response to fluid flow through the passage from said space to the outside of said sleeve.

2. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a uid inlet through which pressure liuid may flow into the interior space of the sleeve between said one end of the latter and the adjacent end of the piston, the wall of the sleeve having a port through which said fluid may flow from said space, means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said adjacent end of the piston overlies said port, said piston being movable toward the other end of said sleeve against the action of said spring to a second position wherein said port uncovered, there being a passage including said port communicating said space to the outside of said sleeve when said piston is in said normal position, valve means carried on the piston for closing said passage in response to uid ow through the passage from said space to the outside of said sleeve, and cooperating hammer and anvil means on the sleeve and piston which are engageable to produce an impact upon movement of the piston to at least one of said positions.

3. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a uid inlet through which pressure uid may flow into the interior space of the sleeve between said one end of the latter and the adjacent end of the piston, the wall of the sleeve having a port through which said uid may flow from said space, means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said adjacent end of the piston overlies said port, said piston being movable toward the other end of said sleeve against the action of said spring to a second position wherein said port is uncovered, there being a passage including said port communicating said space to the outside of said sleeve when said piston is in said normal position, valve means carried on the piston for closing said passage in response to fluid ow through the passage from said space to the outside of said sleeve, and cooperating hammer and anvil means on the sleeve and piston which are engageable to produce an impact upon movement of said piston to each of said positions.

4. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a fluid inlet through which pressure tiuid may iiow into the interior space of the sleeve between said one end of the latter and the adjacent end of the piston, the wall of the sleeve having a port through which said uid may flow from said space, a pair of springs acting in opposite directions between said sleeve and piston for biasing the latter to a normal position wherein said adjacent end of the piston overlies said port, said piston being movable toward the other end of said sleeve against the action of one of said springs to a second position wherein said port is uncovered, there being a passage including said port communicating said space to the outside of said sleeve when said piston is in said normal position, and valve means carried on the piston for closing said passage in response to fluid flow through the passage from said space to the outside of said sleeve.

5. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a fluid inlet through which pressure fluid may flow into the interior space of the sleeve between said one end of the latter and the adjacent end of the piston, the wall of the sleeve having a port through which said fluid may flow from said space, means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said adjacent end of the piston overlies said port, said piston being movable toward the other end of said sleeve against the action of said spring to a second position wherein said port is uncovered, there being a passage including said port communicating said space to the outside of said sleeve when said piston is in said normal position, valve means carried on the piston for closing said passage in response to fluid iiow through the passage from said space to the outside ot said sleeve, said piston having a reduced axial passage opening through its opposite ends, and said other end of the sleeve having a discharge opening.

6. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a uid inlet and a restricted orifice through which pressure uid may ow into the interior space of the sleeve between said one end of the latter and the adjacent end of the piston, the wall of the sleeve having a port through which said uid may flow from said Space,

means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said 'adjacent end of the piston overlies said port, said piston being movable toward theother end of said sleeve against the action of s-aid spring to a second position wherein said port is uncovered, there being a passage including said port communicating said `space to the outside of said sleeve when said piston is in said normal position, and valve means carried on the piston for closing said passage in response to uid ow through the passage from said space to lthe outside of said sleeve.

7. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a fluid inlet through which pressure duid may ilow into the interior space `of the sleeve between said one end of the latter and the adjacent end of the piston, the wall of the sleeve having `a port through which said uid may ow from said space, means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said adjacent end of the piston overlies said port, said piston being movable toward the other end of said sleeve against the action of said spring yto a second position wherein said port is uncovered, there being a passage including said port communieating said space to the outside of said sleeve when said piston is in said normal position, valve means carrried on the piston for closing said passage in reponse to fluid flow through `the passage from said space to the outside of said sleeve, a second sleeve encircling and spaced from said rst-mentioned sleeve, end walls joining and closing opposite ends of the space between said sleeves, said port communicating with said latter space, and said rst-mentioned sleeve having a second port in its wall communicating said latter space to the interior of the latter sleeve at the other end of the piston and a discharge opening in said other end of the latter sleeve.

8. In a vibratory jar, a sleeve `closed at one end, a piston slidable in said sleeve, said one end of the sleeve having a fluid inlet through which pressure fluid may flow into the interior space of said sleeve between said one end of the latter and the adjacent end of the piston, the Wall of sad sleeve having a port through which said uid may ow from said space, an axially extending, radially exible valve finger on said adjacent end of the piston, said nger being longitudinally aligned with said port and normally slightly spaced from the inner wall of said sleeve, means including a spring `acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a nonmal position wherein said valve finger overlies said port, the space between the inner wall of the sleeve and said nger in the normal uniiexed condition of the latter forming a restricted passage communicating said space and port when said piston is in its normal position, said finger being exed outwardly against the inner wall of said sleeve to close said por-t in response to the pressure differential created across vthe iinger -by ow of fluid through said passage to said port when said piston is in its normal position, and said piston being movable toward the other end of said sleeve against the action of said spring to a second position wherein said port is uncovered.

9. In a vibratory jar, a sleeve closed at one end, a piston slidable in said sleeve, said one end of the sleeve having a fluid inlet through which pressure fluid may flow into the interior space of said sleeve between said one end of the latter and the adjacent end of the piston, the wall of said sleeve having a plurality of ports spaced approximately the same distance from said one end of the sleeve through which said fluid may How from said space, a plurality of axially extending, radially iiexible valve lingers on said adjacent end of the piston, each of said ngers being longitudinally aligned with one of said ports and normally slightly spaced from the inner wall meuf;

of said sleeve, means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said valve fingers overlie said ports, the space between the inner wall ofthe sleeve and said ingers in the normal unflexed condition of the latter forming a restricted annular passage communicating said space and ports when said piston is in its normal position, said lingers being eXed outwardly against the inner Wall of said sleeve to close said ports in response to the pressure differential created across the lingers by flow of iiuid through said passage to said ports when said piston is in its normal position, and said piston being movable toward the other end of said sleeve against the action of said spring to a second position wherein said ports are uncovered.

l0. In a vibratory jar, a sleeve closed at one end, a piston slidable in the sleeve, said one end of the sleeve having a -uid inlet through which pressure iluid may ow into the interior space of the sleeve between said 20 one end of the latter and the adjacent end of the piston, the wall of the sleeve having a port through which said fluid may flow from said space, means including a spring acting between said sleeve and piston for biasing the latter in the direction of said one end of the sleeve to a normal position wherein said adjacent end of the piston overlies said port, said piston being movable to- Ward the other end of said sleeve against the action of said spring to a second position wherein said port is uncovered, said adjacent end of the piston being slightly reduced and spaced from the inner Wall of the sleeve to form a restricted annular passage which communicates said space and port when said piston is in said normal position, said adjacent end of the piston being axially bored and slotted to form `a radially flexible valve finger overlying said port in the normal position of the piston, said linger being normally spaced from said port and being flexed outwardly against the inner Wall of the sleeve to close the port in response to the pressure dilerential created across said linger by ow of fluid through said passage to said port when said piston is in said normal position, and said linger uncovering said port when said piston is in said second position.

References Cited in the le of this patent UNITED`STATES PATENTS 701,391 Pruszkowski June 3, 1902 2,580,203 Topanelian Dec. 25, 1951 25 2,620,162 Pennington Dec. 2, 1952 2,73 8,956 Bielstein Mar. 20, 1956 

